This invention relates to a valve and spring arrangement for an engine and more particularly to an improved compact engine construction that permits the use of multiple valves.
It is well known that the performance of an internal combustion engine can be increased by employing a greater number of valves for each cylinder. The use of additional valves increases the volumetric efficiency of the engine. For that reason it has been the normal practice to employ four valves per cylinder in high performance engines. Recently, however, certain problems associated with the use of more than four valves per cylinder have been overcome through the valve placement that permits a compact combustion chamber and high compression ratios while still permitting the use of five valves per cylinder. However, as the number of valves per cylinder increases, there are additional problems in connection with the engine layout and particularly with the components associated with the valve train.
Specifically, if multiple valves are employed and they are all operated by a single camshaft, then the placement of the valve springs and their association with the bearings for the associated camshaft can present some problems. That is, it is important to provide a good bearing support for the camshaft so that it will not distort. However,,-the normal practice is to form the bearing journals in the cylinder head and bearing caps associated with it. Wherein the valves are closely placed to each other and wherein multiple bearings are employed for the camshaft, the camshaft bearings can interfere with the placement of the valve springs. Although relocation of the valves could solve this problem, it is necessary to correctly position the valves so as to achieve the desired combustion chamber configuration.
It is, therefore, a principal object of this invention to provide an improved valve and spring arrangement for a multiple valve engine.
It is a further object of this invention to provide a multiple valve spring arrangement for an engine wherein the valve springs can be installed and removed without interference from other components of the engine.
As has been noted, the use of five valves per cylinder which incorporates three intake valves has been found to provide extremely good performance for an engine. However, if the three intake valves are all operated by independent cam lobes, it is desirable to provide bearings between the cam lobes and on opposite sides of the center cam lobe. However, this is very close to the positioning of the center intake valve. Prior art constructions have made it difficult to locate and install the valve spring for the center intake valve where such a bearing arrangement is employed.
It is, therefore, a further object of this invention to provide an improved bearing and spring arrangement for a multiple valve engine wherein the camshaft can be adequately supported and the associated valve springs still easily installed and replaced.
With regard to the aforenoted problems, it is also desirable to be able to provide a relatively large diameter spring for operating on the valves. Normally the spring bears directly against the cylinder head and this involves machining the cylinder head surface to a diameter equal to the maximum diameter of the spring to achieve the desired bearing surface. With the aforenoted space problems, this machining can give rise to additional problems.
It is, therefore, a further object of this invention to provide a improved cylinder head and valve spring construction wherein the valve spring can have a large bearing area but wherein the machining of the cylinder head is facilitated.